(1) Field of Invention
The present invention relates to a cellular material and, more particularly, to an ultra-light micro-lattice and a method for forming the same.
(2) Description of Related Art
Low-density materials are often formed by introducing significant porosity into an architected constituent solid. The effective properties of these highly porous materials are defined both by their cellular architecture (the spatial configuration of voids and solid) and the properties of the solid constituent (e.g. stiffness, strength, etc.). Some materials that currently exist in the ultra-light regime below 10 mg/cc are traditional foams and aerogels. Previously, silica aero gel held the record for lowest density material at 1 mg/cc (See the List of Cited Literature References, Literature Reference No. 1). However, recent innovations have led to the development of aerographite, which is on record as the lowest density material at 0.2 mg/cc (See Literature Reference No. 24). Other ultra-light materials include carbon nanotube aero gel with a density of 4 mg/cc (See Literature Reference No. 2), metallic foams with densities as low as 10 mg/cc (See Literature Reference Nos. 3 and 4) and polymer foams reaching 8 mg/cc (See Literature Reference Nos. 5 and 6). Such ultra-light materials are highly desired for specific strength and stiffness, energy absorption, thermal insulation, damping, acoustic absorption, active cooling and energy storage, and provide excellent solutions for a variety of multifunctional applications (See Literature Reference No. 7). The existing ultra-low-density materials mentioned above have random cellular architectures, with mechanical performance dominated by bending of internal ligaments, resulting in specific properties far below those of the bulk constituent (See Literature Reference No. 7). The only exception in the ultra-light regime are honeycomb structures, which have a periodic architecture and excellent mechanical properties, but are highly anisotropic and reach their fabrication limit at ˜10 mg/cc (See Literature Reference No. 8). To maximize the mechanical properties such as strength, stiffness, and energy absorption of a cellular material for a given constituent solid, cellular architectures must be formed that are ordered and mechanically efficient. Deshpande et al. have demonstrated that ligament bending can be suppressed in suitably designed ordered, truss-like cellular architectures, resulting in stretching dominated mechanical behavior, with a significant increase in effective elastic modulus and strength (See Literature Reference No. 9).
However, none of the currently available techniques result in a material with ultra-low densities (e.g., less than 0.1% relative density) and a lattice cellular architecture that can enable a material with the desired strength and the ability to achieve recoverable deformation. Thus, a continuing need exists for an ultra-light micro-lattice and a method for forming such a lattice that possesses an ultra-low relative density and also possesses the ability to achieve recoverable deformation.